Why different batteries give different runtimes?

HighLumens

Enlightened
Joined
Nov 17, 2008
Messages
394
Location
Italy
Hi all,
I was wondering why you get longer runtimes by using Lithium batteries and shorter ones if you use rechargeables.

For example in a normal rechargeable i read 1.2 v and 550 mAh: of course there are less volts (in a normal alkaline there are 1.5 v) and probably less mAh (a normal alkaline doesn' t show the mAh) but what makes a battery giving more runtime than another one? Volts? mAh? Both?
I am very confused about it.

Thanks
 

wesinator

Newly Enlightened
Joined
Dec 8, 2008
Messages
75
Location
Louisville, Kentucky
mAh (capacity) is the runtime part, and volts are much juice a battery can push out at one time, and some rechargeable rcr123a batteries have a higher voltage than primary batteries and can short out the circuitry of some flashlights. they also have about half the capacity. i prefer primaries myself.
 

Mockingbird

Newly Enlightened
Joined
Jun 24, 2006
Messages
161
"what makes a battery giving more runtime than another one? Volts? mAh? Both?" Both. If a device requires say 3.6 volts to operate properly, then one 3.6 volt 550 mah battery will power it for the same amout of time as three 1.2 volt 550 mah batteries in series (end to end). One 1.2 volt 550 mah battery would power a device for the same amount of time, but only if that device required only 1.2 volts to operate properly. The amount of amps required from the device figures in there too, but maybe you get the idea.
 

Marduke

Flashaholic
Joined
Jun 19, 2007
Messages
10,110
Location
Huntsville, AL
Total stored energy is volts x capacity. Are you interested in NiMH or Li-Ion or lithium primaries? You are mixing units so I am not sure which chemistry you want to know about.

In the AA and AAA form factor, rechargables give more runtime than most primaries. In the CR123 form factor, rechargables give less runtime than primaries.
 

HighLumens

Enlightened
Joined
Nov 17, 2008
Messages
394
Location
Italy
When i wrote 1,2v 550mAh i was talking about a AAA battery

"In the AA and AAA form factor, rechargables give more runtime than most primaries"

yeah, now I understand why (in a review of the LD01 (AAA) on another site) rechargeables were better..

"mAh (capacity) is the runtime part, and volts are much juice a battery can push out at one time"

So if I want to get the best runtime from a Fenix LD01 (AAA) I have to use a 1,5v (as required by Fenix) AAA battery with as many mAh as possible,right?

But why don' t lithiums and alkalines show the mAh part? I can' t see that written anywhere on the batteries, but I think lithiums have a huge amount of mAh (about double runtime than alkalines:twothumbs)!!
 

Mr Happy

Flashlight Enthusiast
Joined
Nov 21, 2007
Messages
5,390
Location
Southern California
But why don' t lithiums and alkalines show the mAh part? I can' t see that written anywhere on the batteries, but I think lithiums have a huge amount of mAh (about double runtime than alkalines
It's partly because the mAh is not a single number. It varies with how you measure it.

In the case of NiMH, there is a standard method for measuring the mAh capacity, and manufacturers can quote that without too much confusion.

With alkaline batteries, the mAh figure can be more than twice as much at low drain than at high drain. It also can vary according to whether you run the battery intermittently or continuously. Therefore no single number is really applicable. You can, however, download data sheets from the manufacturers giving graphs with all the technical information.

To some extent the same is true of lithium primaries. They have a more constant mAh capacity under varying loads, but there is still no industry standard way of measuring it.

Most of the time manufacturers put less information on packaging rather than more, because they think most people will not know how to interpret the numbers and will get confused about them. We can see this with battery voltages; we just have to look at the number of times people ask about alkaline batteries being 1.5 volts and rechargeable batteries being 1.2 volts. In fact neither battery is 1.5 volts or 1.2 volts, but explaining why that is would not fit on the side of a battery.
 

HighLumens

Enlightened
Joined
Nov 17, 2008
Messages
394
Location
Italy
It's partly because the mAh is not a single number. It varies with how you measure it.

In the case of NiMH, there is a standard method for measuring the mAh capacity, and manufacturers can quote that without too much confusion.

With alkaline batteries, the mAh figure can be more than twice as much at low drain than at high drain. It also can vary according to whether you run the battery intermittently or continuously. Therefore no single number is really applicable. You can, however, download data sheets from the manufacturers giving graphs with all the technical information.

To some extent the same is true of lithium primaries. They have a more constant mAh capacity under varying loads, but there is still no industry standard way of measuring it.

Most of the time manufacturers put less information on packaging rather than more, because they think most people will not know how to interpret the numbers and will get confused about them.
Great explanation, thanks!

We can see this with battery voltages; we just have to look at the number of times people ask about alkaline batteries being 1.5 volts and rechargeable batteries being 1.2 volts. In fact neither battery is 1.5 volts or 1.2 volts, but explaining why that is would not fit on the side of a battery.
I think I'm one of them :p : I didn't understand this part at all "but explaining why that is would not fit on the side of a battery"; what do you mean?

I know I'm asking lots of things, but I'm totally new at this kind of things and words :oops:
 

Mr Happy

Flashlight Enthusiast
Joined
Nov 21, 2007
Messages
5,390
Location
Southern California
I think I'm one of them :p : I didn't understand this part at all "but explaining why that is would not fit on the side of a battery"; what do you mean?
The voltage obtained from a given type of battery depends on the amount of charge remaining in it and the amount of current being drawn from it.

If you look in the sticky "Threads of Interest" at the top of this forum, you can find in there various threads with "Battery Shoot Out" in their title. Take a glance through some of those threads, and you will see graphs of battery voltage against time at various loads. You will see that the voltage varies quite a lot between full and empty. You will also see that the shape of those graphs varies a bit between NiMH, alkaline and lithium batteries.

Because of all this complexity, there is too much information to condense down into one number. Therefore, the industry just picks an "average" kind of voltage to write on the battery label. It is only a description for convenience to let people identify what battery they have.
 
Last edited:

Marduke

Flashaholic
Joined
Jun 19, 2007
Messages
10,110
Location
Huntsville, AL
The " 1,2v 550mAh" confused me, because that's EXTREMELY low even for an AAA cell. A NiMH AAA cell is typically between 800-1000mAh.

For all around performance in the AA and AAA format, it would be best to get a smart charger and some Eneloop cells.
 

LuxLuthor

Flashaholic
Joined
Nov 5, 2005
Messages
10,629
Location
MS
I think you would get a lot of your questions answered by looking at www.batteryuniversity.com I don't say this to put you off. It is really worth checking out. Just read what you are interested in and go back and add to your knowledge later when motivated. That site gives you a wonderful foundation that very few people using batteries will ever have.
 

Marduke

Flashaholic
Joined
Jun 19, 2007
Messages
10,110
Location
Huntsville, AL
aaa eneloop are only 800 mAh? can't I find them with 1000mAh?


No, regular high capacity cells can reach that high, but they self discharge much quicker, and are more delicate cells. That's why I said for best all around performance, Eneloops are the best.
 

HighLumens

Enlightened
Joined
Nov 17, 2008
Messages
394
Location
Italy
I think eneloops are the best if you don' t use often the device that uses them(the batteries will not discharge on their own), but if you use a lot that device, then you had better use normal rechareables with 1000 mAh because you will discharge the batteries before they self discharge.
 

Marduke

Flashaholic
Joined
Jun 19, 2007
Messages
10,110
Location
Huntsville, AL
I think eneloops are the best if you don' t use often the device that uses them(the batteries will not discharge on their own), but if you use a lot that device, then you had better use normal rechareables with 1000 mAh because you will discharge the batteries before they self discharge.


Depends on the device. LSD is not Eneloop's only plus. They maintain a higher discharge voltage than other brands. This makes them ideal for voltage sensitive devices, such as those designed specifically for alkaline cells.

They are also more robust, taking more abuse and still maintaining capacity and cycles. Standardizing on them also makes logistics easier. You don't have to maintain two separate sets of cells for different devices.

Eneloop also do not inflate their specs. What you see on the label is a minimum. With some other brands, what you see on the label is an impossible imaginary number which in no way reflects what the cell actually does. I have yet to see an actual "1000 mAh" AAA cell.


They are the best general use cell.
 

Patriot

Flashaholic
Joined
Feb 13, 2007
Messages
11,254
Location
Arizona
Sounds like you got most of your questions answered but I did want to back up Marduke's thoughts about the Eneloops. I haven't used a better rechargeable yet and have been using them in flashlights, cameras, and radio transmitters since they came out. They've outperformed the Duracell and Energizer batteries in AA and AAA format.
 
Top